Power supply circuit



F. SAAR Jul 23, 1935.

POWER SUPPLY CIRCUIT Filed April 15, 1953 INVENT OR FEA VZ 6144/? BY g ATTORNEY Patented July 23, 1935 UNITED STATES PATENT OFFICE POWER SUPPLYCIRCUIT Germany Application April 13, 1933, Serial No. 665,945 InGermany April 8, 1932 1 Claim.

5 from the inner circuit elements enclosed within an outer casing orcabinet as soon as the casing is opened as when it is desired to changean amplifier tube or any other circuit element. In the customaryarrangements a special switch is provided for this purpose in additionto operating on and off switch for the apparatus. The special switchacts upon opening of the protective casing or cabinet to interrupt thecurrent supply line and thus leave the apparatus without current eventhough the operating switch may be turned on. In this way the danger ofelectrical shocks is eliminated.

The present invention describes an improvement for such apparatus.According to the invention the apparatus is provided with one switchonly whose contact halves are movable relative to each other both by thehandle of the on and oh switch and by means of an interrupting memberacting during the opening of the protective cover or cabinet. Theadvantage obtained by the present invention resides in the fact that theapparatus requires only the one switch which is used for the generaloperation of the set as well as for interrupting the voltage supplyduring the opening of the protective cover, a measure necessary for thesake of safety.

An embodiment of the invention is shown in the drawing by way ofexample.

In the drawing Figure 1 illustrates an end view of a preferred form ofthe invention wherein the safety switch device cooperates with the onand off switch of an amplifier; and,

Figure 2 is a back view of the device shown in Figure 1.

Z designates the supply lead, G is the casing or cabinet of theapparatus. The switch provided is a double pole switch comprising twocontact halves K, K" connected with the operating handle B (seeFigure 1) as well as two contact springs K1, K2. The latter are operatedby an interrupting member connected with the removable portion of thecabinet as for instance the rear of the cabinet or protective casing G.In its simplest embodiment this interrupting member may consist of a rodD of insulating material and acts to displace the contacts into aposition in which closing with the other switch halves is possible onlywhen the protective casing is in the proper position. Instead of makingthe rod D of insulating material it is also possible to use a metallicinterrupting member which rests against corresponding insulating platesat the contact springs.

It will be seen from considering the drawing that if the removableportion G of the cabinet is removed, say for the purpose of replacing aworn out tube, the rod D which is attached to the removable portion Gwill be pulled out along with the removable panel. When this happens thespring contacts K1 and K"2 will drop down out of range of the topcontacts so that even if the on and oil switch. B is operated to turnthe power on, it is impossible for the contacts K and K to contact withthe spring contacts K1 and K"2 respectively. It is obvious that if theon and ofi switch B is in the on position, contact will be broken whenthe removable portion G is taken out. The rod D is shaped so as tofacilitate operating the two lower spring contacts when the portion G ofthe cabinet is in its proper position. For this purpose it will be notedthat the rod D is tapered toward the outer end thereof.

I claim:

In amplifying apparatus and the like of the type provided with aprotective casing having a section thereof displaceable for opening thecasing so as to permit access to the apparatus and with means forenergizing the amplifying apparatus by connection thereof to a source ofenergizing potential, an on and off switch for connecting anddisconnecting the apparatus to the energizing source, means cooperatingwith the displaceable section of the casing for rendering the switchinoperative to connect the apparatus to the source when the casing isopen said on and off switch including at least two cooperating contactsadapted to contact with one another to close the energizing circuit,both of said two cooperating contacts being movable with respect to thecasing, one thereof being manually operable, the displaceable section ofthe casing being provided with means cooperating with the other of saidcontacts for shifting said other contact from its normal position in adirection to prevent the two contacts closing the circuit between theapparatus and the power source when the casing is opened.

FRANZ SAAR.

